JPH10173444A - Power voltage switch circuit for amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power consumption without impairing the follow-up ability of a power source for an output signal by changing the detection voltage of the output signal to a high voltage when the output signal frequency of an amplifier is low, and changing the detection voltage of the output signal to a low voltage when the output signal frequency is high. SOLUTION: When the base potential of a transistor 41 is higher than the base potential of a transistor 42, the transistor 41 is turned on, and the transistor 42 is turned off. Then, the power voltage supplying system of an amplifier 2 is switched from a low voltage side power supply terminal 7 to a high voltage side power supply terminal 8, and a high voltage power source is supplied to the amplifier 2. At that time, the base potential of the transistor 41 is changed according to the frequency of an output signal by the output voltage of the amplifier 2 and a detection voltage setting capacitor 34. That is, when the frequency of the output signal of the amplifier 2 is low, the output signal detection voltage of the amplifier 2 is set to a high voltage, and when the frequency of the output signal is high, the output signal detection voltage of the amplifier 2 is set to a low voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply voltage switching circuit for an amplifier.

[0002]

2. Description of the Related Art In a conventional amplifier, an output voltage of the amplifier is detected for the purpose of reducing power consumption.
A switching circuit is added to switch the power supply voltage of the amplifier to the high voltage side when the detected voltage is equal to or higher than the set value, and to switch to the low voltage side when the detected voltage is equal to or lower than the set value.

[0003]

However, in such a conventional power supply voltage switching circuit of an amplifier, since the power supply voltage is switched by a change in the output voltage of the amplifier, when the frequency of the output signal of the amplifier becomes high, The ability to follow the switching of the power supply to the output signal deteriorates, and the output signal is distorted. Further, if the detection voltage of the output signal is set low so as not to distort the output signal, there is a problem that power consumption cannot be reduced by switching and using the power supply voltage of the amplifier.

The present invention has been made in view of the above circumstances, and changes the detection voltage of an output signal to a high voltage when the output signal frequency of the amplifier is low, and changes the detection voltage to a low voltage when the output signal frequency is high. It is another object of the present invention to provide a power supply voltage switching circuit for an amplifier that can reduce power consumption without impairing the ability of the power supply to follow an output signal.

[0005]

SUMMARY OF THE INVENTION In order to solve this problem, the power supply voltage of the amplifier of the present invention is switched by setting the output signal detection voltage of the amplifier to a high voltage when the frequency of the output signal of the amplifier is low. And output signal voltage detection means for detecting the detection voltage of the amplifier by setting the output signal detection voltage of the amplifier to a low voltage when the frequency of the output signal of the amplifier is high,
A comparison means for comparing a detection voltage detected by the output signal voltage detection means with a preset reference value, and outputting a power supply switching signal when the detection voltage becomes equal to or higher than the reference value; And switching means for operating the power supply voltage supplied to the amplifier from a low voltage side to a high voltage side.

Accordingly, the output signal detection voltage of the amplifier is set to a high voltage when the frequency of the output signal is low, and is set to a low voltage when the frequency of the output signal is high, which impairs the ability of the power supply to follow the output signal. Power consumption can be reduced.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to a first aspect of the present invention, there is provided an amplifier for amplifying an input signal, and a power supply for switching a plurality of power supply voltages to the amplifier in accordance with a change in a detection voltage of the amplifier. A voltage switching circuit, wherein when the frequency of the output signal of the amplifier is low, the output signal detection voltage of the amplifier is set to a high voltage, and when the frequency of the output signal of the amplifier is high, the output signal detection voltage of the amplifier is low. An output signal voltage detecting means for detecting a detection voltage of the amplifier by setting the voltage, a detection voltage detected by the output signal voltage detecting means is compared with a preset reference value, and the detection voltage is equal to or higher than the reference value. Comparison means for outputting a power supply switching signal at times, and switching means operated by the power supply switching signal of the comparison means for switching a power supply voltage supplied to the amplifier from a low voltage side to a high voltage side. Is intended the difference between the low voltage side power supply voltage by setting the output signal detection voltage of the amplifier to a high voltage at low frequency of the output signal becomes small, the effect of reducing power consumption is achieved. Further, when the output signal detection voltage of the amplifier is set to a low voltage when the frequency of the output signal is high, the difference between the output signal detection voltage and the low-voltage side power supply voltage is increased, and the followability of the power supply voltage to the output signal is improved.

According to a second aspect of the present invention, when the detected voltage detected by the output signal voltage detecting means is equal to or lower than a reference value, the power supply voltage supplied to the amplifier is switched to a lower voltage side. The power supply voltage supplied to the amplifier is
It is possible to switch between a low voltage side and a high voltage side in response to a change in the detection voltage of the amplifier.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG.

FIG. 1 is a circuit diagram of a power supply voltage switching circuit of an amplifier according to an embodiment of the present invention. In the figure, the power supply voltage switching circuit includes an amplifier 2, an output signal voltage detection circuit 3, a comparison circuit 4, and a switching circuit 5. Amplifier 2
Amplifies the input signal input from the input terminal 1 and outputs the amplified signal to the output terminal 6.

The output signal voltage detection circuit 3 sets the output signal detection voltage of the amplifier 2 to a high voltage when the frequency of the output signal of the amplifier 2 is low, and outputs the output of the amplifier 2 when the frequency of the output signal of the amplifier 2 is high. The detection voltage setting resistors 32 and 33 are connected in series between the output terminal of the amplifier 2 and the ground via a diode 31 for half-wave rectification which also prevents backflow, and the detection voltage setting. It comprises a detection voltage setting capacitor 34 connected in parallel with the resistor 32 and a series circuit of a frequency variable amplitude limiting resistor 35.

The comparison circuit 4 compares the detection voltage detected by the output signal voltage detection circuit 3 with a predetermined reference value, and outputs a power supply switching signal when the detection voltage becomes equal to or higher than the reference value. The transistor 41 includes a transistor 41 that uses a detection voltage detected by the signal voltage detection circuit 3 as a base bias, and a transistor 42 that uses a reference voltage set by reference voltage setting resistors 43 and 44 as a base bias. It is connected to the switching circuit 5 via the resistor 45. The emitters of the transistor 41 and the transistor 42 are connected to ground via a common current limiting resistor 46, and the collector of the transistor 42 is connected to the low voltage side power supply terminal 7 via a current limiting resistor 47. The reference voltage setting resistors 43 and 44 generate a reference voltage by dividing the low voltage supplied to the low voltage side power supply terminal 7.

The switching circuit 5 comprises a transistor 51 connected between the high-voltage side power supply terminal 8 and the power supply terminal of the amplifier 2, and a malfunction prevention resistor 52 connected between the base and the emitter of the transistor 51. , Transistor 5
The base of 1 is connected to the collector of the transistor 41 of the comparison circuit 4. The low-voltage power supply terminal 7 is connected between the power supply terminals of the amplifier 2 via a backflow prevention diode 9.

In this configuration, an input signal input from the input terminal 1 is amplified by the amplifier 2 and output to the output terminal 6. The output signal voltage of the amplifier 2 is set and detected by the output signal voltage detection circuit 3, and this detection voltage is applied to the base of the transistor 41 of the comparison circuit 4. Then, the low-voltage side power supply voltage is set to the reference voltage setting resistors 43 and 44.
Is applied to the base of the transistor 42. In this state, when the base potential of the transistor 41 becomes higher than the base potential of the transistor 42,
The transistor 41 turns on and the transistor 42 turns off. When the transistor 41 is turned on, the switching circuit 5
Is turned on, the power supply voltage supply system of the amplifier 2 is switched from the low voltage side power supply terminal 7 to the high voltage side power supply terminal 8.
, And the amplifier 2 is supplied with high-voltage power.

At this time, the base potential of the transistor 41 depends on the output voltage of the amplifier 2 and the detection voltage setting capacitor 34.
Changes according to the frequency of the output signal. That is, when the frequency of the output signal of the amplifier 2 is low, the output signal detection voltage of the amplifier 2 is set to a high voltage, and when the frequency of the output signal of the amplifier 2 is high, the output signal detection voltage of the amplifier 2 is low. Is set to

FIG. 2 shows the relationship between the output signal detection voltage and the power supply voltage when the frequency of the output signal is low in this embodiment. Reference numeral 21 denotes a high-voltage power supply voltage, and 22 denotes a low-high-voltage power supply. , 23 is an output signal waveform, 24 is a ground potential, and 25 is an output signal detection voltage. In FIG. 2, when the frequency of the output signal is low, the output signal detection voltage 25
Becomes higher, and the difference from the lower voltage side power supply voltage 22 becomes smaller. Therefore, the effect of reducing power consumption can be increased.

FIG. 3 shows the relationship between the output signal detection voltage and the power supply voltage when the frequency of the output signal is high in the present embodiment, where 26 is a high voltage side power supply voltage, and 27 is a low high voltage side power supply. , 28 is an output signal waveform, 29 is a ground potential, and 30 is an output signal detection voltage. In FIG. 3, when the frequency of the output signal is high, the output signal detection voltage 30
And the difference from the low-voltage side power supply voltage 27 increases. Therefore, the ability of the power supply voltage to follow the output signal is improved.

[0018]

As described above, according to the present invention, the output signal detection voltage for switching the power supply voltage of the amplifier is set to a high voltage when the frequency of the output signal is low, and is set to a low voltage when the frequency of the output signal is high. Can be set to voltage. As a result, the power supply voltage can be switched according to the change in the output signal frequency and the output signal voltage, and the power consumption can be reduced without impairing the followability of the power supply voltage to the output signal when the output signal frequency is high. Is achieved.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a power supply voltage switching circuit of an amplifier according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between an output signal detection voltage and a power supply voltage when the frequency of the output signal is low in the embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between an output signal detection voltage and a power supply voltage when the frequency of the output signal is high in the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input terminal 2 Amplifier 3 Output signal voltage detection circuit 4 Comparison circuit 5 Switching circuit 6 Output terminal 7 Low voltage side power supply terminal 8 High voltage side power supply terminal

Claims (2)

[Claims] 1. An amplifier for amplifying an input signal, and a power supply voltage switching circuit for switching and connecting a plurality of power supply voltages to the amplifier in response to a change in an output signal voltage of the amplifier, the amplifier comprising: When the frequency is low, the output signal detection voltage of the amplifier is set to a high voltage, and when the frequency of the output signal of the amplifier is high, the output signal detection voltage of the amplifier is set to a low voltage to detect the output signal voltage of the amplifier. Output signal voltage detection means, comparing the detection voltage detected by the output signal voltage detection means with a preset reference value,
A comparison means for outputting a power supply switching signal when the detected voltage becomes equal to or higher than a reference value; and a switching means for being operated by a power supply switching signal of the comparison means and switching a power supply voltage supplied to the amplifier from a low voltage side to a high voltage side And a power supply voltage switching circuit for an amplifier. 2. The amplifier according to claim 1, wherein the power supply voltage supplied to the amplifier is switched to a low voltage side when the detected voltage detected by the output signal voltage detecting means is equal to or lower than a reference value. Power supply voltage switching circuit.